Electrolyte forming process for a metal-supported solid-oxide fuel cell

Abstract

A process for forming an electrolyte for a metal-supported solid-oxide fuel cell, the process comprising: a. applying a doped-ceria green electrolyte to an anode layer; b. removing any solvents and organic matter from the green electrolyte; c. pressing the green electrolyte to increase green electrolyte density; and d. heating the green electrolyte at a rate of temperature increase whilst in the temperature range 800° C.-1000° C. of in the range 5-20° C./minute to form the electrolyte, together with an electrolyte obtained by the process, a fuel cell and fuel cell stack, comprising the electrolyte, and the use of the fuel in the generation of electrical energy.

The invention claimed is: 
     
       1. A process for forming a metal-supported solid-oxide fuel cell comprising:
 providing a metal-supported anode layer comprising an anode layer that has been applied to a flat metal substrate; 
 forming an electrolyte on the metal-supported anode layer using a process comprising:
 a. applying a doped-ceria green electrolyte to the metal-supported anode layer; 
 b. removing any solvents and organic matter from the green electrolyte; 
 c. pressing the green electrolyte to increase green electrolyte density; 
 d. applying a pinning mass to at least part of the part of the metal substrate onto which neither an anode nor an electrode material has been applied to hold the metal substrate flat during sintering; and 
 e. heating the green electrolyte at a rate of temperature increase whilst in the temperature range 800° C. to 1000° C. of in the range 5° C./minute to 20° C./minute to sinter the green electrolyte to form the electrolyte and thereafter removing the pinning mass; and 
 
 applying a cathode material to the electrolyte. 
 
     
     
       2. The process according to  claim 1 , further comprising: forming the doped-ceria green electrolyte from a screen-printable ink. 
     
     
       3. The process according to  claim 1 , wherein the flat metal substrate comprises a perforated region surrounded by a non-perforated region. 
     
     
       4. The process according to  claim 1 , wherein removing any solvents and organic matter from the green electrolyte comprises evaporating the solvents. 
     
     
       5. The process according to  claim 1 , wherein removing any solvents and organic matter comprises heating the green electrolyte to a temperature in the range of 250° C. to 500° C. until the organic matter has decomposed. 
     
     
       6. The process according to  claim 1 , wherein the anode layer is a sintered anode layer. 
     
     
       7. The process according to  claim 1 , wherein the anode layer is a green anode layer and the green anode layer and green electrolyte are sintered in a single firing step. 
     
     
       8. The process according to  claim 1 , wherein the green electrolyte comprises multiple layers of electrolyte formed by applying the green electrolyte in layers over the anode layer, with drying between the application of each layer of the green electrolyte. 
     
     
       9. The process according to  claim 1 , wherein pressing of the green electrolyte comprises application of a pressure in the range of 50 MPa to 500 MPa. 
     
     
       10. The process according to  claim 1 , wherein the electrolyte covers the anode layer and the flat metal substrate. 
     
     
       11. The process according to  claim 1 , wherein electrolyte layer covers the anode layer and another portion of the flat metal substrate that is not covered by the anode layer. 
     
     
       12. The process according to  claim 1 , wherein the heating the green electrolyte is performed in air. 
     
     
       13. The process according to  claim 1 , wherein pressing is achieved using cold isostatic pressing or uniaxial bladder pressing. 
     
     
       14. The process according to  claim 1 , wherein the metal substrate is a stainless steel substrate. 
     
     
       15. The process according to  claim 1 , wherein the temperature of step e. is less than 1100° C. 
     
     
       16. The process according to  claim 1 , wherein step e. is performed in air. 
     
     
       17. The process according to  claim 4 , wherein the step of evaporating the solvents comprises evaporation at a temperature in the range 100° C. to 250° C. 
     
     
       18. A process for forming a metal-supported solid-oxide fuel cell comprising:
 providing a metal-supported anode layer comprising an anode layer that has been applied to a flat metal substrate;
 wherein the flat metal substrate comprises a ferritic stainless steel foil substrate made partially porous in its central region, such that the flat metal substrate comprises a perforated region surrounded by a non-perforated region; 
 wherein the anode layer has been deposited as a film on the foil substrate; 
 
 forming an electrolyte on the metal-supported anode layer using a process comprising:
 a. applying a doped-ceria green electrolyte to the metal-supported anode layer; 
 b. removing any solvents and organic matter from the green electrolyte; 
 c. pressing the green electrolyte to increase green electrolyte density; 
 d. applying a pinning mass to at least part of the non-perforated region of the metal substrate onto which neither an anode nor an electrode material has been applied to hold the metal substrate flat during sintering; and 
 e. heating the green electrolyte at a rate of temperature increase whilst in the temperature range 800° C. to 1000° C. of in the range 5° C./minute to 20° C./minute to sinter the green electrolyte to form the electrolyte, and thereafter removing the pinning mass; 
 wherein the heating the green electrolyte is performed in air; and 
 
 applying a cathode material to the electrolyte.